Electromagnetic fuel injection system for internal-combustion engines

ABSTRACT

RISES, THE GROUPS OF THE CONTROL COILS AND THUS THE FUEL INJECTION VALVE ARE SWITCHED SO AS TO BE ENERGIZED SIMULTANEOUSLY. THE CONTROL COILS OF FUEL INJECTION VALVES, ONE COIL TO ONE VALVE, ARE ELECTRICALLY CONNECTED TO FORM A PLURALITY OF COIL GROUPS. DURING THE LOW-SPEED OPERATION OF THE ENGINE, SAID GROUPS OF COILS ARE SEQUENTIALLY ENERGIZED SO THAT THE VALVES ALTERNATE IN THEIR INJECTION ACTION. WHEN THE SUM OF THE COIL ENERGIZING DURATION AND A CERTAIN PREDETERMINED DURATION EXCEEDS THE DURATION PROPORTIONAL TO THE TIME REQUIRED BY ENGINE TO COMPLETE ONE REVOLUTION AS THE SPEED OF THE ENGINE

United States Patent Inventors Takashl lnoue;

Takao Masuth; Takeshi Harada, Higashi- Matsuyama-shi, Japan Appl. No. 868,388 Filed Oct. 22, 1969 Patented June 28, 1971 Assignee Diesel Klki Kabushiki Kaisha Tokyo, Japan Priority Oct. 30, 1968 Japan ELECTROMAGNETIC FUEL INJECTION SYSTEM FOR INTERNAL-COMBUSTION ENGINES 7 Claims, 2 Drawing Figs.

U.S. Cl 123/32, 123/! 19, 123/139 Int. Cl. F02d 5/02 Field ofSeareh 123/32 (E),

References Cited UNITED STATES PATENTS 3,522,794 8/1970 Reichardt 123/32 Primary Examiner-Mark M. Newman Y Assistant Examiner-Cort R. Flint At!0rney-Otto John Munz ABSTRACT: The control coils of fuel injection valves, one coil to one valve, are electrically connected to form a plurality of coil groups. During the low-speed operation of the engine, said groups of coils are sequentially energized so that the valves alternate in their injection action. When the sum of the coil energizing duration and a certain predetermined duration exceeds the duration proportional to the time required by engine to complete one revolution as the speed of the engine rises, the groups of the control coils and thus the fuel injection valve are switched so as to be energized simultaneously.

PATENTEU JUN28 [9n INVENTONS 1. ELECTROMAGNETIC FUEL ECTION SYSTEM FOR INTERNAL-CQMBUSTION ENGINES This invention relates to the electromagnetic fuel injection system and, in particular, to an electromagnetic fuel injection system for internal combustion engines of the type in which fuel injection is effected selectively for engine cylinders by switching between one number of cylinders and another number in ratio of l to 2.

In conventional electromagnetic fuel injection systems, fuel injection quantity is controlled by means of the energizing du ration T in which voltage is applied to electromagnetic or solenoid type injection valves. As the engine r.p.rn. N rises, the control duration 1 (=60/N second), i.e., the duration in which fuel injection quantity can be controlled, shortens and may become shorter than the energizing duration T to result in temporary loss of control.

According to the conventional system, fuel injection is effected simultaneously into the intake pipes of all of the cylinders in the four-stroke cycle engine, so that it could occur that, in some cylinders at a certain time during operation, the intake and the exhaust valve are both open, presenting a condition of so-called valve overlap" to allow the fuel-air mixture to partially escape direct into the exhaust line. Such escape is particularly wasteful during low-speed engine operation and increases the overall fuel consumption of the engine.

In order to overcome the shortcomings of the conventional system noted in the above, we proposed, by our Japanese Pat. application 47098/68, to divide the engine cylinders into two or more groups; to reduce the number of cylinders simultaneously receiving fuel in low-speed engine operation, that is, when the control duration t is relatively large, in such a way as to minimize or avoid the concurrence of injection timing with said valve overlap in the respective cylinders; and to increase the number of simultaneously fuel-receiving cylinders, when the engine is running fast, in order to prolong, in an equivalent and relative sense, the control duration t, which is then relatively short.

In the method proposed, the change of the number of simul taneously energized injection valves is to be effected at a predetermined level'of engine speed by means of a switch operating in response to engine speed. Then, even a short energizing duration T, meaning a small injection quantity, can be adequately varied for control purpose even if the engine is running'fast as long as there is a sufficient time margin or leeway due to the difference between a short duration T and a long duration t. But when the duration T is made very long, the temporary loss of control might result even when the engine is running slowly. In other words, the method of switching from one number of simultaneously fuel-receiving cylinders to the other at a predetermined r.p.rn. level does not reckon with the controllability of energizing duration T at all speeds of the engine.

The object of the present invention is to provide an improvement over the method previously proposed by this inventor, and contemplates addition of some predetermined length of duration to the energizing duration T and effecting said switching just when the sum of these two durations increases to exceed the duration, of which mention will be made later, proportional to the time required by engine crankshaft to complete one revolution, so that said switching will not entail such temporary loss of control as was stated in the above. Said additional duration is to be determined on the basis of desired time range within which the duration T for injection fuel can be varied.

Stated briefly, the electromagnetic fuel injection system according to the present invention comprises a means of closing a circuit at the moment the sum of the energizing duration proportional to the time required by engine crankshaft to complete one revolution, and also pulse shunting circuits for bypassing and thereby making ineffective the pulses trains by which the solenoids or coils of said injection valves are otherwise caused to operate for fuel injection, so that all of the injection valve solenoids'wili b'e energized simultaneously when and if said sum exceeds the duration for one crankshaft revolution.

For the switching means, this inventor prefers to use a thyristor and two transistors so adapted and combined that one of the two transistors changes to positive the polarity of voltage applying across said thyristor, from its anode to cathode, immediately and instantly after said duration for one crankshaft revolution lapses, while the other transistors applies positive voltage to the thyristor gate during that portion of said predetermined duration following the energizing duration T. As the two transistors so operate, the thyristor becomes ready to conduct when said sum of the two durations increases to match, or become equal to, the duration for one crankshaft revolution.

The pulse shunting circuits should preferably contain diodes for blocking the shunting paths there with to defeat said shunting action. These diodes are to become conductive to shunt the the pulse trains when said switching means starts conductmg. 7

Moreover, the system according to the invention preferably includes a circuit which reduces, when said switching means becomes conductive, the frequency of the pulse in said trains, each pulse being the determinant of the length of energizing duration T. This circuit is to halve the frequency of fuel injection concurrent with a switching from alternate two-cylinder injection to four-cylinder injection in a four-cylinder engine, for example, and thus equalizes injection quantities prior and subsequent to the switching.

The invention will be further explained, and other features will become apparent, from the following description, with reference to the accompanying drawings, in which:

FIG. 1 is the circuit diagram of a system according to the invention, and FIG. 2 is a line diagram for illustrating the operations of the system.

Referring now to FIG. 1, section A is a converter of known type for translating the revolving speed of the engine into a pulse voltage; section B is a monostable multivibrator of known type, generating square-wave pulses whose signal frequency is proportional to the speed of the engine and whose signal width varies with the vacuum in the engine intake line; section D is an output amplifier for controlling the energization of the fuel injection valves on the engine; section C is a selector for selecting the number of injection valves by switching for simultaneous injection; and block E is a smoothing circuit of any known type.

Section A comprises switches 8,, 8,, which are actuated from the cam in the breaker of the engine; condensers C,, 0,; and resistors r, through r inclusive. Resistor r, has its one end connected to conductor W, leading from the positive side of the power source, not shown, and other end to the movable contact of switch 8,, whose stationary contact is connected to conductor W, leading from the negative side of said power source. Similarly, resistor r has its one end connected to conductor W, and other end to the movable contact of switch 8,, whose stationary contact is connected to conductor W Between conductors W, and W are located dividers composed of resistors r,, r, and resistors r,,, r,,. Connection point J, is between resistors r and r another connection point J is between resistors r and r Condenser C, is connected between said point J, and switch 8,, and condenser C between point I, and a circuit in sections C and D.

The monostable multivibrator, or section B, comprises such timing elements as transistors Tr,, Tr transformer L, and resistors R R,. The emitters of these transistors are connected direct to conductor W The collector of transistor Tr, is connected to W, through resistor r, and to W through resistors r,,, r,,. A branch circuit formed of series-connected resistor R,, 3, D and resistor R is connected between W, and W,. The base of transistor Tr, is connected to the connection point between said resistor R and diode D Transistor Tr, has its emitter connected direct to W base to the connection point between r, and r,,, and collector to W, through the primary winding L, of transformer L and resistors r,,,. A divider circuit, consisting of resistors R R is formed between conductors W, and W, The secondary winding L has its one end connected to the connection point between R,, and R and other end connected, through diode D to the connection point W between resistor R, and diode D,,. The core, not shown, of transformer L is so adapted as to be displaced in position by diaphragm D,, which moves in response to changes in negative pressure or vacuum in the engine intake pipe P. By this displacement of the core, the inductance of transformer L is varied in response to changes in vacuum. The connection point W is connected to said points J, and I, through a respective diode, D, for J, and D, for 1,.

Section D comprises two sets of transistors, Tr, and Tr,, for one set and Tr and Tr,, for the other set, with which are associated, in two sets, resistors r, through r,,, inclusive, and control coils, L, through L inclusive, for the solenoid type fuel injection valves. Transistor Tr has its emitter connected direct to conductor W collector is connected, through resistor r,,, to conductor W, and, through resistors r,,, and r,,, to conductor W and base is connected, through resistors r,,,, r,, and conductor l,, to the movable contact of switch S, and, through resistor r,,, to the terminal U, leading to the collector of transistor Tr, Transistor Tr, has its emitter connected to conductor W base is connected to the connection point between resistors r,, and r,,; and collector is connected to one end of the parallel control coils L,, L,. The other end of these parallel coils is connected direct to conductor W,. The other half of section D, comprising transistors Tr Tr,,, is formed in the same way as the half thus far described, the difference being that the one end of resistor r,,, is connected, through conductor 1,, to the movable contact of switch 8,.

Section C comprises control resistors Tr Tr and switching-action thyristor SCR for controlling the selection of the number of injection valves for simultaneous injection. Thyristor SCR has its cathode connected direct to conductor W, and anode to conductor W, through resistor R,,. Transistor Tr, is connected across thyristor SCR, with its emitter tied to the cathode side and collector to the anode side. The base of this transistor is connected to the connection point between resistors R, andR The outer end of R, is connected to conductor W and the outer end of R,, to the conductor 1 Transistor Tr has its emitter connected direct to conductor W and collector to the connection point U, between R and R,,,. Resistors R,.,, R, together with resistors R constitute a divider as located between W, and W Into the connection point between R and R,., is tied the gate of thyristor SCR, The base of transistor Tr is connected to the point between resistor R and the cathode of diode D,,,, the outer end of resistor R being connected to W, and the anode end of diode D being connected, through resistor R,,,, to conductor W, and, through condenser C and resistor R,,,, to the collector of transistor Tr,,. The anode of thyristor SCR is connected to smoothing circuit E, which leads through two separate paths to the connection point between resistor r,,, and r, through diode D and to the point between resistors r,,, and r,, through diode D Having thus far described the circuit arrangement of the system, the operations of the circuit components for accomplishing the objects of the invention will be explained in reference to FIGS. 1 and 2, first by assuming the switching-action thyristor SCR to be in nonconductive state. It should be noted that the cathode side of diodes D D, is kept at positive potential by the smoothing circuit E, so that positive voltages due to the opening of switches S,, S, will not apply to the thyristor SCR side through these diodes to interfere with the normal operation of transistors Tr,,, Tr,,.

Switches 8,, S, in the r.p.m.-voltage conversion circuit open and close alternately when the engine is running. Suppose switch S, has just closed: by this closure, negative voltage applies from conductor W to the base of transistor Tr, through resistors r,,, r,, and conductor 1, and, at the same time, condenser C, discharges. The discharge current of condenser C,, which has been charged from positive-potential W,, flows through switch S, and resistor r,, causing the potential of connection point 1, to turn negative. The negative potential of J, enables diode D, to conduct, thereby generating a trigger pulse, and changes the potential of connection point W to negative. By this negative potential, diode D becomes held in blocking state to apply negative voltage to the base of transistor Tr,. Consequently, transistor Tr, becomes nonconductive and, under this condition, a positive voltage determined by the ohmic sizes of divider resistors r r r applies to the base of transistor Tr,. As transistor Tr, conducts, current flows in the primary coil L, of transformer L to induce voltage in secondary coil L By this induction, current flows through resistors R R,, diode D and coil L, to increase the voltage drop across resistor R, and thus makes the base of transistor Tr, more negative. These events constitute a positive feedback.

The current due to the induced voltage, which decreases exponentially, holds the base of Tr, negative and maintains transistor Tr, in conductive state until the current falls exponentially to and below a predetermined value. It will be noted that the primary current inducing a secondary current is a function of the time constant of the primary-side reactance and resistance. Since the reactance varies with the position of the transformer core, and because the core displaces itself in response to a change in the engine intake pipe vacuum, the width of the pulse T occurring at the connection point U, varies with said vacuum.

Because the bases of transistors Tr,,, Tr,, are connected to point U,, the pulse T gives a negative potential to these bases for the duration of the pulse. Because switch S is open at this juncture, the base of transistor Tr,, has been kept to positive potential. During the period of T therefore, two negative pulses are applying to the base of Tr, to make this transistor nonconductive, while the base of Tr,, is receiving the negative pulse and a positive pulse due to switch 8, in open position. The net result of the negative and the positive pulse at the base of Tr,, is positive, because of the divider circuit, so that this transistor conducts. Thus, the nonconducting Tr, causes transistor Tn, to conduct and the conducting Tr,, causes Tr to stay nonconductive. With the current so conducted by Tr coils L,, L, become energized to effect fuel injection by their valves.

As switch S, opens, switch S, closes. By the opening of switch 8,, a positive voltage applies through resistor r,, conductor 1,, resistors r,,,, r,, to the base of transistor Tr,,; and by the closure of switch 8,, negative voltage applies through switch 8,, negative voltage applies through switch S conductor l resistors r,,, r,-, to the base of transistor Tr, At the same time, the condenser C,, which has been charged from the positive conductor W, through resistor r,, conductor resistor r,,, and conductor 1 discharges. The discharge current flows through resistor r,,, condenser C conductor 1 resistor r, and switch S to turn to negative the potential of connection point J As a result, a trigger pulse, inducted by conduction through diode D applies to connection point W, just as in the case of the closure of switch S, considered previously. This pulse gives rise to a negative pulse T at point U,, which applies to the base of transistors Tr,,, Tr,, to make Tr, conductive and Tr,, nonconductive, so that, while Tr becomes nonconductive, Tr becomes conductive to energize coils L,, L, for effecting fuel injection by their valves. in the present instance, it should be recalled that coils L,, L, and coils L L, are in two respective sets, and each set of coils with their injection valves are energized simultaneously to perform simultaneous fuel injection. These sets alternate in the sequence of fuel injection. This manner of injection will hereafter be referred to, for brevity, as two-cylinder injection.

Next, the operation of the system with thyristor SCR in conductive state will be explained. As switch S, closes and opens, a square-wave pulse having its width corresponding to the duration of closure applies to the base of transistor Tr through its base resistor R to keep this transistor in OH state. The resultant voltage across the emitter and collector is indicated as voltageU FIG. 2, and identical to the square-wave pulse whose duration is T By this voltage, the anode of thyristor SCR becomes positive in polarity with respect to its cathode.

Now, the potential of terminal M illustrated at U in FIG. 2 is that of the collector transistor Tr,,, and changes according as solenoids L L are energized or not. When the potential M becomes positive, current flows into condenser C through resistor R to charge the condenser. This charging is quick because resistor R is sized small in ohmic value, and takes place through the path including said R C diode D base and emitter of transistor Tr As the potential of terminal M becomes negative, condenser C discharges through the path including R C and R While this discharging current is flowing, the base of transistor Tr stays negative with respect to the emitter and keeps this transistor in off state. The duration of the off state is determined by the time constant of the discharge circuit, that is, mainly of C and R,,,; and the duration of the pulse voltage arising from this off state of transistor Tr across its collector and emitter is due to said time constant and corresponds to duration T of voltage U As will be noted in FIG. 2, square-wave pulse U immediately follows pulse U If the sum duration of T and T exceeds the duration T which is the duration proportional to the time required for one revolution of engine crankshaft, as stated at the onset, thyristor SCR will conduct, because thyristor gate is at a positive voltage determined by the ohmic value of divider resistors R R while a positive voltage is across the thyristor anode and cathode due to switch 8, being in closed state at this time. A thyristor SCR so conducting signifies that control of injection quantity by alternate two-cylinder injection is temporarily lost. To circumvent this condition, the number of simultaneously injecting valves must be increased and, at the same time, the frequency of injection must be reduced in proportion to theincrease in the number of valves so that the said excess will disappear to revive control of injection quantity, that is, to make the control duration 1 effective. These requirements are met in the present invention in the following manner.

With thyristor SCR conducting as above, the trains of pulses arriving from switches 8,, S at the bases of transistors Tr Tr for energizing the solenoids flow through diodes D D and thyristor SCR into the negative conductor W and, as a result, the bases of these transistors remain at negative potential to cause transistors Tr and Tr to conduct simultaneously, thereby energizing both sets of solenoids L L and L L,. In the illustrated instance, the circuit from diodes D D to thyristor SCR shunts the bases of transistor Tr Tr to the thyristor and, by so shunting, switches from alternate twocylinder injection to simultaneous four-cylinder injection.

Note that one end of condenser C is connected to the base of transistor Tr so thatthe train of pulses arriving from switch S is shunted to the negative conductor W, when the thyristor is in conductive state. This means that one of the two trigger pulses generated by the monostable multivibrator is eliminated to halve the trigger pulse frequency and thus double the interval between two successive pulses. The net effect of the doubled interval is obviously the unchanged fuel injection quantity through the transition from alternate twocylinder injection to simultaneous four-cylinder injection.

Although alternate two-cylinder injection and simultaneous fourcylinder injection are considered in the above description of the system illustrated in the drawing, it will be readily seen from the spirit of the invention that the present invention can be applied to the switching between three cylinders and six cylinders, even between one cylinder and two cylinders in a four cylinder engine, or between any two numbers of cylinders as long as the ratio of the numbers is l to 2.

We claim:

1. An electromagnetic fuel injection system for internal combustion engines, having a plurality of injection valve control coils electrically connected to form a plurality of independent coil groups which are alternately energized during the low-speed operation and simultaneously energized during the high-speed operation of the engine, comprising: a switching means which becomes conductive when the sum of the duration for energizing said control coils and a predetermined duration corresponding to the injection quantity control range exceeds the duration proportional to the time required by engine crankshaft to complete one revolution, and a pulse shunting circuit which, when said switching means becomes conductive, shunts the pulse trains used to alternately energize the said groups of coils, so that said control coil groups become energized simultaneously.

2. A system according to claim 1, in which the switching means is composed of a thyristor and two transistors, one of said transistors being adapted to turn to positive the polarity of the voltage impressed across the anode and cathode of said thyristor upon termination of the duration proportional to the time required by engine crankshaft to complete one revolution, and the other transistor being adapted to apply a positive voltage to the gate of said thyristor during the predetermined duration corresponding the injection quantity control range upon tennination of the duration for applying energizing voltage to said control coils.

3. A system according to claim 1, in which the pulse shunting circuit includes diodes shunting the trains of pulses used to alternately energize said control coil groups through said switching means.

4. An electromagnetic fuel injection system for an internal combustion engine, having a plurality of injection valve control coils electrically connected to form a plurality of independent coil groups which are alternately energized during the low-speed operation and simultaneously energized during the high-speed operation of the engine, comprising: a first transistor connecting said control coil groups respectively to the source of voltage; a second transistor for controlling said first transistor, to which are applied as input signals, a first pulse voltage having a pulse frequency proportional to engine running speed and a pulse width varying with the vacuum in the engine intake pipe and a second pulse voltage for alternately energizing said control coil groups; a switching means which becomes conductive at the moment the sum of the duration for energizing said control coils and a predetermined duration corresponding to the injection quantity control range exceeds the duration proportional to the time required by engine crankshaft to complete one revolution; and a pulse shunting circuit which, when said switching means becomes conductive, shunts the pulse trains used to alternately energize the said groups of coils, so that said control coil groups become energized simultaneously.

5. A system according to claim 4, in which the switching means is composed of a thyristor and two transistors, one of said transistors being adapted to turn to positive the polarity of the voltage impressed across the anode and cathode of said thyristor upon termination of the duration proportional to the time required by engine crankshaft to complete one revolution, and the other transistor being controlled with the output of said second transistor through a time constant circuit comprising a capacitor and resistor and adapted to apply, upon termination of the duration for applying voltage to and thereby energizing said control coils, a positive voltage to the gate of said thyristor during the predetermined duration corresponding to the injection quantity control range.

6. A system according to claim 4, in which the pulse shunting circuit includes diodes shunting said second pulse voltage through said thyristor.

7. An electromagnetic fuel injection system for internal combustion engines, having a plurality of injection valve control coils electrically connected to form a plurality of independent coil groups which are alternately energized during the low-speed operation and simultaneously energized during the high-speed operation of the engine, comprising: a switching means which becomes conductive when the sum of the duration for energizing said control coils and a predetermined duration corresponding the injeetion quantity control range exceeds the duration proportional to the time required by engine simultaneously; and a circuit which reduces, when said switching means conducts, the frequency of the pulse voltage determining the. duration for applying energizing voltage to said control coils. 

